High Inbreeding
Despite the fact that the Amish do not intentionally marry their relatives, there is a substantial chance of inbreeding in their communities. The fact that Amish households are so small means that when it comes to marrying another Amish person, they don’t have much of a choice.
No Recruits
Another unique element of the Amish is their adamant opposition to evangelization and religious conversion. Their tradition of banning non-members and isolating themselves from the contemporary world is well-established in the organization. It comes as no surprise, then, that the Amish are unwilling to accept recruits. Furthermore, even the most fervent supporters of the Amish are unable to become members of the church.